Process of making hydrocyanic acid.



UNITED STATES PATENT OFFICE.

JULIUS BUEB, OF DESSAU, GERMANY, ASSIGNOR TO THE ROESSLER 8a IIASSLACHERCHEMICAL COMPANY, OF NE? YORK, N. Y.

SPECIFICATION forming part of Letters Patent No. 642,782, dated February6, 1900.

Application filed October 1, 1898. $erial No. 692,391. (No specimens.)

T0 aZZ whom it may concern.-

Be it known that I, J ULIUsBUEB, a subject of the Emperor of Germany,and a resident of Dessau, Germany, have invented certain new and usefulImprovements in Recovering Hydrocyanic Acid from Gases ContainingCyanogen, of which the following is a specification.

This invention relates to the production of hydrocyanic acid from gases(other than coalgas) containing cyanogensuch, for example, as the gasesobtained by the dry distillation of molasses or residues resulting fromsugarmaking. The invention is also applicable to the separation ofsynthetically-form ed hydrocyanic acid from other gases combinedtherewith. In dealing with such gases various difficulties have hithertobeen encountered in separating from them the hydrocyanic acid as such,more particularly in effecting its separation from carbonic acid, andhitherto it has been necessary in order to extract hydrocyanic acid fromthe gases in question to adopt the same course as that which has to befollowed in obtaining cyanogen from coal-gas, the cyanogen being firstseparated in the form of a double ferro-cyanogen salt and then convertedinto the required alkaline compound of cyanogen. The presentinventionenables this indirect process to be replaced by a process permitting thesaid gases to be freed from their hydrocyanic acid direct, such acidbeing then, when required, converted into the alkaline compound byanother direct operation.

In carrying out this invention the gases to be treated are cooled, andif they contain ammonia they are conducted through diluted sulphuricacid-say at twenty per cent.which will absorb the ammonia. Thesulphate-of-ammonia lye thus obtained, which by the gradual addition ofconcentrated sulphuric acid may be made to contain as much as fromtwentyeight to thirtyper cent. of (NH )2SO is then evaporated to convertit into solid sulphate of ammonia. The gases freed from ammonia areconducted through a tower or vessel in contact with a current ofhigh-grade alcohol passing in the opposite direction. The alcoholexercises its selective action upon the hydrocyanogen contained in thegases and separates such acid from the gases and dissolves it, so thatan alcoholic solution of hydrocy-- cyanic-acid vapor which has beendistilled oif through chambers containing alcoholic caustic alkali. Whenthe hydrocyanic acid and caustic alkali meet, the cyanogen alkali,scarcely soluble in alcohol, becomes precipitated in the form of a whitepowder. The alcohol which distils through and is free from hydrocyanicacid is condensed and can be again utilized in the tower for the purposeof absorbing hydrocyanic acid. The chambers containing the alcoholiccaustic alkaline lye are disconnected after the lye has been used up anddischarged upon a strainer, having been allowed to cool first, ifnecessary. After straining a certain amount of cyanogen alkali remainsupon the strainer, and this on being dried will be found to contain fromninety-six to ninety-eight per cent. of pure cyanogen salt. The alkalilye running 0% from the strainer, containing from two to four per cent.of cyanogen alkali, is placed in a saturator in front of thealcohol-tower, and the gases containing cyanogen from which hydrocyanicacid is to be separated passing through it precipitate the alkali intheform of an alkaline carbonate, while the alcohol becomes saturated withhydrocyanic acid.-

The carbonate of alkali precipitated after having been strained anddried will contain ninety-nine per cent. of carbonate. The alcoholcontaining hydrocyanic acid is treated in the manner hereinbeforedescribed.

The hereinbefore-described process may be .used in all cases to whichfrom its nature it is applicable and where the object is to sepa ratehydrocyanic acid as such from gas or gas mixtures containing cyanogen.

I claim 1. The process for separating hydrocyanic acid directly fromgases resulting from the destructive distillation of organic matters,which consists in subjecting such gases to contact with a current ofalcohol passing in the opposite direction, substantially as described.

2. The process for separating h ydrocyanic acid directly from gasesresulting from the destructive distillation of organic matters, whichconsists in subjecting such gases to contact with a current of alcoholpassing in the opposite direction, and subjecting the alcoholic solutionof hydrocyanic acid thus formed to fractional distillation,substantially as described.

3. The process for separating hydrocyauic acid from gases resulting fromthe destructive distillation of organic matters, which consists insubjecting such gases to contact with alcohol, subjecting the alcoholicsolution of hydrocyanic acid thus formed to fractional distillation, andreacting upon the hydrocyanic-acid gas with alcoholic causticalkali,substantially as described.

t. The process of separating hydrocyanic acid from gases resulting fromthe destructive distillation of organic matters, which consists insubjecting such gases to contact with alcohol, subjecting the alcoholicsolution of hydrocyanic acid thus formed to fractional distillation,separating the hydrocyanic-acid gas from the alcohol by reaction withalcoholic caustic alkali, straining off the alkali lye containingcyanogen alkali salt from the precipitate, reacting upon this mother-lyewith the distillation-gases, and subjecting the hydrocyanic acid thusliberated, with the distillation-gases, to contact with alcohol,substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

JULIUS BUEB.

Witnesses:

FRANZ IIASSLACHER, l\[ICHAEL VoLK.

